X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcDeriv.lhs;h=7a2954a6d5a4307c9e459904c93667623ec928e4;hp=d414c6f3f3cbddb4442c02f650f2d740263a4669;hb=9319fbaf14f420cbbd9e670093cc86c5f04b7800;hpb=08efb089bb9a1a9c77df6caefe15b44d6ab5b2d3 diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs index d414c6f..7a2954a 100644 --- a/compiler/typecheck/TcDeriv.lhs +++ b/compiler/typecheck/TcDeriv.lhs @@ -46,6 +46,7 @@ import SrcLoc import Util import ListSetOps import Outputable +import FastString import Bag \end{code} @@ -86,8 +87,13 @@ data DerivSpec = DS { ds_loc :: SrcSpan type EarlyDerivSpec = Either DerivSpec DerivSpec -- Left ds => the context for the instance should be inferred - -- (ds_theta is required) - -- Right ds => the context for the instance is supplied by the programmer + -- In this case ds_theta is the list of all the + -- constraints needed, such as (Eq [a], Eq a) + -- The inference process is to reduce this to a + -- simpler form (e.g. Eq a) + -- + -- Right ds => the exact context for the instance is supplied + -- by the programmer; it is ds_theta pprDerivSpec :: DerivSpec -> SDoc pprDerivSpec (DS { ds_loc = l, ds_name = n, ds_tvs = tvs, @@ -222,6 +228,9 @@ And then translate it to: Note [Newtype deriving superclasses] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +(See also Trac #1220 for an interesting exchange on newtype +deriving and superclasses.) + The 'tys' here come from the partial application in the deriving clause. The last arg is the new instance type. @@ -253,79 +262,106 @@ when the dict is constructed in TcInstDcls.tcInstDecl2 tcDeriving :: [LTyClDecl Name] -- All type constructors -> [LInstDecl Name] -- All instance declarations -> [LDerivDecl Name] -- All stand-alone deriving declarations - -> TcM ([InstInfo], -- The generated "instance decls" + -> TcM ([InstInfo Name], -- The generated "instance decls" HsValBinds Name) -- Extra generated top-level bindings tcDeriving tycl_decls inst_decls deriv_decls - = recoverM (returnM ([], emptyValBindsOut)) $ + = recoverM (return ([], emptyValBindsOut)) $ do { -- Fish the "deriving"-related information out of the TcEnv -- And make the necessary "equations". ; early_specs <- makeDerivSpecs tycl_decls inst_decls deriv_decls ; overlap_flag <- getOverlapFlag ; let (infer_specs, given_specs) = splitEithers early_specs - ; (insts1, aux_binds1) <- mapAndUnzipM (genInst overlap_flag) given_specs + ; insts1 <- mapM (genInst overlap_flag) given_specs - ; final_specs <- extendLocalInstEnv (map iSpec insts1) $ + ; final_specs <- extendLocalInstEnv (map (iSpec . fst) insts1) $ inferInstanceContexts overlap_flag infer_specs - ; (insts2, aux_binds2) <- mapAndUnzipM (genInst overlap_flag) final_specs + ; insts2 <- mapM (genInst overlap_flag) final_specs ; is_boot <- tcIsHsBoot - ; rn_binds <- makeAuxBinds is_boot tycl_decls - (concat aux_binds1 ++ concat aux_binds2) - - ; let inst_info = insts1 ++ insts2 + -- Generate the generic to/from functions from each type declaration + ; gen_binds <- mkGenericBinds is_boot + ; (inst_info, rn_binds) <- renameDeriv is_boot gen_binds (insts1 ++ insts2) ; dflags <- getDOpts - ; ioToTcRn (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" - (ddump_deriving inst_info rn_binds)) + ; liftIO (dumpIfSet_dyn dflags Opt_D_dump_deriv "Derived instances" + (ddump_deriving inst_info rn_binds)) ; return (inst_info, rn_binds) } where - ddump_deriving :: [InstInfo] -> HsValBinds Name -> SDoc + ddump_deriving :: [InstInfo Name] -> HsValBinds Name -> SDoc ddump_deriving inst_infos extra_binds = vcat (map pprInstInfoDetails inst_infos) $$ ppr extra_binds -makeAuxBinds :: Bool -> [LTyClDecl Name] -> DerivAuxBinds -> TcM (HsValBinds Name) -makeAuxBinds is_boot tycl_decls deriv_aux_binds - | is_boot -- If we are compiling a hs-boot file, - -- don't generate any derived bindings - = return emptyValBindsOut +renameDeriv :: Bool -> LHsBinds RdrName + -> [(InstInfo RdrName, DerivAuxBinds)] + -> TcM ([InstInfo Name], HsValBinds Name) +renameDeriv is_boot gen_binds insts + | is_boot -- If we are compiling a hs-boot file, don't generate any derived bindings + -- The inst-info bindings will all be empty, but it's easier to + -- just use rn_inst_info to change the type appropriately + = do { rn_inst_infos <- mapM rn_inst_info inst_infos + ; return (rn_inst_infos, emptyValBindsOut) } | otherwise - = do { let aux_binds = listToBag (map genAuxBind (rm_dups [] deriv_aux_binds)) - -- Generate any extra not-one-inst-decl-specific binds, + = discardWarnings $ -- Discard warnings about unused bindings etc + do { (rn_gen, dus_gen) <- setOptM Opt_PatternSignatures $ -- Type signatures in patterns + -- are used in the generic binds + rnTopBinds (ValBindsIn gen_binds []) + ; keepAliveSetTc (duDefs dus_gen) -- Mark these guys to be kept alive + + -- Generate and rename any extra not-one-inst-decl-specific binds, -- notably "con2tag" and/or "tag2con" functions. + -- Bring those names into scope before renaming the instances themselves + ; loc <- getSrcSpanM -- Generic loc for shared bindings + ; let aux_binds = listToBag $ map (genAuxBind loc) $ + rm_dups [] $ concat deriv_aux_binds + ; rn_aux_lhs <- rnTopBindsLHS emptyFsEnv (ValBindsIn aux_binds []) + ; let aux_names = map unLoc (collectHsValBinders rn_aux_lhs) + + ; bindLocalNames aux_names $ + do { (rn_aux, _dus) <- rnTopBindsRHS aux_names rn_aux_lhs + ; rn_inst_infos <- mapM rn_inst_info inst_infos + ; return (rn_inst_infos, rn_aux `plusHsValBinds` rn_gen) } } - -- Generate the generic to/from functions from each type declaration - ; gen_binds <- mkGenericBinds tycl_decls - - -- Rename these extra bindings, discarding warnings about unused bindings etc - -- Type signatures in patterns are used in the generic binds - ; discardWarnings $ - setOptM Opt_PatternSignatures $ - do { (rn_deriv, _dus1) <- rnTopBinds (ValBindsIn aux_binds []) - ; (rn_gen, dus_gen) <- rnTopBinds (ValBindsIn gen_binds []) - ; keepAliveSetTc (duDefs dus_gen) -- Mark these guys to - -- be kept alive - ; return (rn_deriv `plusHsValBinds` rn_gen) } } where + (inst_infos, deriv_aux_binds) = unzip insts + -- Remove duplicate requests for auxilliary bindings rm_dups acc [] = acc rm_dups acc (b:bs) | any (isDupAux b) acc = rm_dups acc bs | otherwise = rm_dups (b:acc) bs + + rn_inst_info (InstInfo { iSpec = inst, iBinds = NewTypeDerived }) + = return (InstInfo { iSpec = inst, iBinds = NewTypeDerived }) + + rn_inst_info (InstInfo { iSpec = inst, iBinds = VanillaInst binds sigs }) + = -- Bring the right type variables into + -- scope (yuk), and rename the method binds + ASSERT( null sigs ) + bindLocalNames (map Var.varName tyvars) $ + do { (rn_binds, _fvs) <- rnMethodBinds clas_nm (\_ -> []) [] binds + ; return (InstInfo { iSpec = inst, iBinds = VanillaInst rn_binds [] }) } + where + (tyvars,_,clas,_) = instanceHead inst + clas_nm = className clas + ----------------------------------------- -mkGenericBinds :: [LTyClDecl Name] -> TcM (LHsBinds RdrName) -mkGenericBinds tycl_decls - = do { tcs <- mapM tcLookupTyCon - [ tc_name | - L _ (TyData { tcdLName = L _ tc_name }) <- tycl_decls] - -- We are only interested in the data type declarations +mkGenericBinds :: Bool -> TcM (LHsBinds RdrName) +mkGenericBinds is_boot + | is_boot + = return emptyBag + | otherwise + = do { gbl_env <- getGblEnv + ; let tcs = typeEnvTyCons (tcg_type_env gbl_env) ; return (unionManyBags [ mkTyConGenericBinds tc | tc <- tcs, tyConHasGenerics tc ]) } - -- And then only in the ones whose 'has-generics' flag is on + -- We are only interested in the data type declarations, + -- and then only in the ones whose 'has-generics' flag is on + -- The predicate tyConHasGenerics finds both of these \end{code} @@ -357,12 +393,12 @@ makeDerivSpecs :: [LTyClDecl Name] -> TcM [EarlyDerivSpec] makeDerivSpecs tycl_decls inst_decls deriv_decls - = do { eqns1 <- mapM deriveTyData $ + = do { eqns1 <- mapAndRecoverM deriveTyData $ extractTyDataPreds tycl_decls ++ [ pd -- traverse assoc data families | L _ (InstDecl _ _ _ ats) <- inst_decls , pd <- extractTyDataPreds ats ] - ; eqns2 <- mapM deriveStandalone deriv_decls + ; eqns2 <- mapAndRecoverM deriveStandalone deriv_decls ; return (catMaybes (eqns1 ++ eqns2)) } where extractTyDataPreds decls = @@ -384,9 +420,11 @@ deriveStandalone (L loc (DerivDecl deriv_ty)) <+> text "theta:" <+> ppr theta <+> text "tau:" <+> ppr tau) ; (cls, inst_tys) <- checkValidInstHead tau + ; checkValidInstance tvs theta cls inst_tys + -- C.f. TcInstDcls.tcLocalInstDecl1 + ; let cls_tys = take (length inst_tys - 1) inst_tys inst_ty = last inst_tys - ; traceTc (text "standalone deriving;" <+> text "class:" <+> ppr cls <+> text "class types:" <+> ppr cls_tys @@ -396,11 +434,11 @@ deriveStandalone (L loc (DerivDecl deriv_ty)) ------------------------------------------------------------------ deriveTyData :: (LHsType Name, LTyClDecl Name) -> TcM (Maybe EarlyDerivSpec) -deriveTyData (deriv_pred, L loc decl@(TyData { tcdLName = L _ tycon_name, - tcdTyVars = tv_names, - tcdTyPats = ty_pats })) - = setSrcSpan loc $ - tcAddDeclCtxt decl $ +deriveTyData (L loc deriv_pred, L _ decl@(TyData { tcdLName = L _ tycon_name, + tcdTyVars = tv_names, + tcdTyPats = ty_pats })) + = setSrcSpan loc $ -- Use the location of the 'deriving' item + tcAddDeclCtxt decl $ do { let hs_ty_args = ty_pats `orElse` map (nlHsTyVar . hsLTyVarName) tv_names hs_app = nlHsTyConApp tycon_name hs_ty_args -- We get kinding info for the tyvars by typechecking (T a b) @@ -418,44 +456,67 @@ deriveTyData _other ------------------------------------------------------------------ mkEqnHelp :: InstOrigin -> [TyVar] -> Class -> [Type] -> Type - -> Maybe ThetaType -- Just => context supplied - -- Nothing => context inferred + -> Maybe ThetaType -- Just => context supplied (standalone deriving) + -- Nothing => context inferred (deriving on data decl) -> TcRn (Maybe EarlyDerivSpec) mkEqnHelp orig tvs cls cls_tys tc_app mtheta | Just (tycon, tc_args) <- tcSplitTyConApp_maybe tc_app - = do { -- Make tc_app saturated, because that's what the - -- mkDataTypeEqn things expect - -- It might not be saturated in the standalone deriving case - -- derive instance Monad (T a) - let extra_tvs = dropList tc_args (tyConTyVars tycon) - full_tc_args = tc_args ++ mkTyVarTys extra_tvs - full_tvs = tvs ++ extra_tvs - - ; (rep_tc, rep_tc_args) <- tcLookupFamInstExact tycon full_tc_args + , isAlgTyCon tycon -- Check for functions, primitive types etc + = do { (rep_tc, rep_tc_args) <- tcLookupFamInstExact tycon tc_args + -- Be careful to test rep_tc here: in the case of families, + -- we want to check the instance tycon, not the family tycon + + -- For standalone deriving (mtheta /= Nothing), + -- check that all the data constructors are in scope + -- By this time we know that the thing is algebraic + -- because we've called checkInstHead in derivingStandalone + ; rdr_env <- getGlobalRdrEnv + ; let hidden_data_cons = isAbstractTyCon rep_tc || any not_in_scope (tyConDataCons rep_tc) + not_in_scope dc = null (lookupGRE_Name rdr_env (dataConName dc)) + ; checkTc (isNothing mtheta || not hidden_data_cons) + (derivingHiddenErr tycon) ; mayDeriveDataTypeable <- doptM Opt_DeriveDataTypeable ; newtype_deriving <- doptM Opt_GeneralizedNewtypeDeriving - -- Be careful to test rep_tc here: in the case of families, we want - -- to check the instance tycon, not the family tycon ; if isDataTyCon rep_tc then - mkDataTypeEqn orig mayDeriveDataTypeable full_tvs cls cls_tys - tycon full_tc_args rep_tc rep_tc_args mtheta + mkDataTypeEqn orig mayDeriveDataTypeable tvs cls cls_tys + tycon tc_args rep_tc rep_tc_args mtheta else mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving - full_tvs cls cls_tys - tycon full_tc_args rep_tc rep_tc_args mtheta } + tvs cls cls_tys + tycon tc_args rep_tc rep_tc_args mtheta } | otherwise = baleOut (derivingThingErr cls cls_tys tc_app - (ptext SLIT("Last argument of the instance must be a type application"))) + (ptext (sLit "The last argument of the instance must be a data or newtype application"))) baleOut :: Message -> TcM (Maybe a) baleOut err = do { addErrTc err; return Nothing } \end{code} -Auxiliary lookup wrapper which requires that looked up family instances are -not type instances. If called with a vanilla tycon, the old type application -is simply returned. +Note [Looking up family instances for deriving] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +tcLookupFamInstExact is an auxiliary lookup wrapper which requires +that looked-up family instances exist. If called with a vanilla +tycon, the old type application is simply returned. + +If we have + data instance F () = ... deriving Eq + data instance F () = ... deriving Eq +then tcLookupFamInstExact will be confused by the two matches; +but that can't happen because tcInstDecls1 doesn't call tcDeriving +if there are any overlaps. + +There are two other things that might go wrong with the lookup. +First, we might see a standalone deriving clause + deriving Eq (F ()) +when there is no data instance F () in scope. + +Note that it's OK to have + data instance F [a] = ... + deriving Eq (F [(a,b)]) +where the match is not exact; the same holds for ordinary data types +with standalone deriving declrations. \begin{code} tcLookupFamInstExact :: TyCon -> [Type] -> TcM (TyCon, [Type]) @@ -465,18 +526,14 @@ tcLookupFamInstExact tycon tys | otherwise = do { maybeFamInst <- tcLookupFamInst tycon tys ; case maybeFamInst of - Nothing -> famInstNotFound tycon tys False - Just famInst@(_, rep_tys) - | not variable_only_subst -> famInstNotFound tycon tys True - | otherwise -> return famInst - where - tvs = map (Type.getTyVar - "TcDeriv.tcLookupFamInstExact") - rep_tys - variable_only_subst = all Type.isTyVarTy rep_tys && - sizeVarSet (mkVarSet tvs) == length tvs - -- renaming may have no repetitions + Nothing -> famInstNotFound tycon tys + Just famInst -> return famInst } + +famInstNotFound :: TyCon -> [Type] -> TcM a +famInstNotFound tycon tys + = failWithTc (ptext (sLit "No family instance for") + <+> quotes (pprTypeApp tycon (ppr tycon) tys)) \end{code} @@ -501,27 +558,13 @@ mkDataTypeEqn orig mayDeriveDataTypeable tvs cls cls_tys = ASSERT( null cls_tys ) mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta -mk_data_eqn :: InstOrigin -> [TyVar] -> Class - -> TyCon -> [TcType] -> TyCon -> [TcType] -> Maybe ThetaType - -> TcM (Maybe EarlyDerivSpec) +mk_data_eqn, mk_typeable_eqn + :: InstOrigin -> [TyVar] -> Class + -> TyCon -> [TcType] -> TyCon -> [TcType] -> Maybe ThetaType + -> TcM (Maybe EarlyDerivSpec) mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta - | cls `hasKey` typeableClassKey - = -- The Typeable class is special in several ways - -- data T a b = ... deriving( Typeable ) - -- gives - -- instance Typeable2 T where ... - -- Notice that: - -- 1. There are no constraints in the instance - -- 2. There are no type variables either - -- 3. The actual class we want to generate isn't necessarily - -- Typeable; it depends on the arity of the type - do { real_clas <- tcLookupClass (typeableClassNames !! tyConArity tycon) - ; dfun_name <- new_dfun_name real_clas tycon - ; loc <- getSrcSpanM - ; return (Just $ Right $ - DS { ds_loc = loc, ds_orig = orig, ds_name = dfun_name, ds_tvs = [] - , ds_cls = real_clas, ds_tys = [mkTyConApp tycon []] - , ds_theta = mtheta `orElse` [], ds_newtype = False }) } + | getName cls `elem` typeableClassNames + = mk_typeable_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta | otherwise = do { dfun_name <- new_dfun_name cls tycon @@ -533,20 +576,51 @@ mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta dataConInstOrigArgTys data_con rep_tc_args, not (isUnLiftedType arg_ty) ] -- No constraints for unlifted types? + -- See Note [Superclasses of derived instance] + sc_constraints = substTheta (zipOpenTvSubst (classTyVars cls) inst_tys) + (classSCTheta cls) + inst_tys = [mkTyConApp tycon tc_args] + stupid_subst = zipTopTvSubst (tyConTyVars rep_tc) rep_tc_args stupid_constraints = substTheta stupid_subst (tyConStupidTheta rep_tc) - all_constraints = stupid_constraints ++ ordinary_constraints - -- see Note [Data decl contexts] above + all_constraints = stupid_constraints ++ sc_constraints ++ ordinary_constraints spec = DS { ds_loc = loc, ds_orig = orig , ds_name = dfun_name, ds_tvs = tvs - , ds_cls = cls, ds_tys = [mkTyConApp tycon tc_args] + , ds_cls = cls, ds_tys = inst_tys , ds_theta = mtheta `orElse` all_constraints , ds_newtype = False } ; return (if isJust mtheta then Just (Right spec) -- Specified context else Just (Left spec)) } -- Infer context +mk_typeable_eqn orig tvs cls tycon tc_args rep_tc _rep_tc_args mtheta + -- The Typeable class is special in several ways + -- data T a b = ... deriving( Typeable ) + -- gives + -- instance Typeable2 T where ... + -- Notice that: + -- 1. There are no constraints in the instance + -- 2. There are no type variables either + -- 3. The actual class we want to generate isn't necessarily + -- Typeable; it depends on the arity of the type + | isNothing mtheta -- deriving on a data type decl + = do { checkTc (cls `hasKey` typeableClassKey) + (ptext (sLit "Use deriving( Typeable ) on a data type declaration")) + ; real_cls <- tcLookupClass (typeableClassNames !! tyConArity tycon) + ; mk_typeable_eqn orig tvs real_cls tycon [] rep_tc [] (Just []) } + + | otherwise -- standaone deriving + = do { checkTc (null tc_args) + (ptext (sLit "Derived typeable instance must be of form (Typeable") + <> int (tyConArity tycon) <+> ppr tycon <> rparen) + ; dfun_name <- new_dfun_name cls tycon + ; loc <- getSrcSpanM + ; return (Just $ Right $ + DS { ds_loc = loc, ds_orig = orig, ds_name = dfun_name, ds_tvs = [] + , ds_cls = cls, ds_tys = [mkTyConApp tycon []] + , ds_theta = mtheta `orElse` [], ds_newtype = False }) } + ------------------------------------------------------------------ -- Check side conditions that dis-allow derivability for particular classes -- This is *apart* from the newtype-deriving mechanism @@ -560,28 +634,27 @@ checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc | notNull cls_tys = Just ty_args_why -- e.g. deriving( Foo s ) | otherwise - = case [cond | (key,cond) <- sideConditions, key == getUnique cls] of - [] -> Just (non_std_why cls) - [cond] -> cond (mayDeriveDataTypeable, rep_tc) - _other -> pprPanic "checkSideConditions" (ppr cls) + = case sideConditions cls of + Just cond -> cond (mayDeriveDataTypeable, rep_tc) + Nothing -> Just non_std_why where - ty_args_why = quotes (ppr (mkClassPred cls cls_tys)) <+> ptext SLIT("is not a class") - -non_std_why :: Class -> SDoc -non_std_why cls = quotes (ppr cls) <+> ptext SLIT("is not a derivable class") - -sideConditions :: [(Unique, Condition)] -sideConditions - = [ (eqClassKey, cond_std), - (ordClassKey, cond_std), - (readClassKey, cond_std), - (showClassKey, cond_std), - (enumClassKey, cond_std `andCond` cond_isEnumeration), - (ixClassKey, cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)), - (boundedClassKey, cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)), - (typeableClassKey, cond_mayDeriveDataTypeable `andCond` cond_typeableOK), - (dataClassKey, cond_mayDeriveDataTypeable `andCond` cond_std) - ] + ty_args_why = quotes (ppr (mkClassPred cls cls_tys)) <+> ptext (sLit "is not a class") + non_std_why = quotes (ppr cls) <+> ptext (sLit "is not a derivable class") + +sideConditions :: Class -> Maybe Condition +sideConditions cls + | cls_key == eqClassKey = Just cond_std + | cls_key == ordClassKey = Just cond_std + | cls_key == readClassKey = Just cond_std + | cls_key == showClassKey = Just cond_std + | cls_key == enumClassKey = Just (cond_std `andCond` cond_isEnumeration) + | cls_key == ixClassKey = Just (cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)) + | cls_key == boundedClassKey = Just (cond_std `andCond` (cond_isEnumeration `orCond` cond_isProduct)) + | cls_key == dataClassKey = Just (cond_mayDeriveDataTypeable `andCond` cond_std) + | getName cls `elem` typeableClassNames = Just (cond_mayDeriveDataTypeable `andCond` cond_typeableOK) + | otherwise = Nothing + where + cls_key = getUnique cls type Condition = (Bool, TyCon) -> Maybe SDoc -- Bool is whether or not we are allowed to derive Data and Typeable @@ -595,7 +668,7 @@ orCond c1 c2 tc Nothing -> Nothing -- c1 succeeds Just x -> case c2 tc of -- c1 fails Nothing -> Nothing - Just y -> Just (x $$ ptext SLIT(" and") $$ y) + Just y -> Just (x $$ ptext (sLit " and") $$ y) -- Both fail andCond :: Condition -> Condition -> Condition @@ -611,9 +684,9 @@ cond_std (_, rep_tc) where data_cons = tyConDataCons rep_tc no_cons_why = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has no data constructors") + ptext (sLit "has no data constructors") existential_why = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has non-Haskell-98 constructor(s)") + ptext (sLit "has non-Haskell-98 constructor(s)") cond_isEnumeration :: Condition cond_isEnumeration (_, rep_tc) @@ -621,7 +694,7 @@ cond_isEnumeration (_, rep_tc) | otherwise = Just why where why = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has non-nullary constructors") + ptext (sLit "has non-nullary constructors") cond_isProduct :: Condition cond_isProduct (_, rep_tc) @@ -629,7 +702,7 @@ cond_isProduct (_, rep_tc) | otherwise = Just why where why = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has more than one constructor") + ptext (sLit "has more than one constructor") cond_typeableOK :: Condition -- OK for Typeable class @@ -643,18 +716,18 @@ cond_typeableOK (_, rep_tc) | otherwise = Nothing where too_many = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has too many arguments") + ptext (sLit "has too many arguments") bad_kind = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has arguments of kind other than `*'") + ptext (sLit "has arguments of kind other than `*'") fam_inst = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("is a type family") + ptext (sLit "is a type family") cond_mayDeriveDataTypeable :: Condition cond_mayDeriveDataTypeable (mayDeriveDataTypeable, _) | mayDeriveDataTypeable = Nothing | otherwise = Just why where - why = ptext SLIT("You need -XDeriveDataTypeable to derive an instance for this class") + why = ptext (sLit "You need -XDeriveDataTypeable to derive an instance for this class") std_class_via_iso :: Class -> Bool std_class_via_iso clas -- These standard classes can be derived for a newtype @@ -666,11 +739,36 @@ std_class_via_iso clas -- These standard classes can be derived for a newtype new_dfun_name :: Class -> TyCon -> TcM Name new_dfun_name clas tycon -- Just a simple wrapper - = newDFunName clas [mkTyConApp tycon []] (getSrcSpan tycon) + = do { loc <- getSrcSpanM -- The location of the instance decl, not of the tycon + ; newDFunName clas [mkTyConApp tycon []] loc } -- The type passed to newDFunName is only used to generate -- a suitable string; hence the empty type arg list \end{code} +Note [Superclasses of derived instance] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +In general, a derived instance decl needs the superclasses of the derived +class too. So if we have + data T a = ...deriving( Ord ) +then the initial context for Ord (T a) should include Eq (T a). Often this is +redundant; we'll also generate an Ord constraint for each constructor argument, +and that will probably generate enough constraints to make the Eq (T a) constraint +be satisfied too. But not always; consider: + + data S a = S + instance Eq (S a) + instance Ord (S a) + + data T a = MkT (S a) deriving( Ord ) + instance Num a => Eq (T a) + +The derived instance for (Ord (T a)) must have a (Num a) constraint! +Similarly consider: + data T a = MkT deriving( Data, Typeable ) +Here there *is* no argument field, but we must nevertheless generate +a context for the Data instances: + instance Typable a => Data (T a) where ... + %************************************************************************ %* * @@ -707,7 +805,7 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs mb_std_err = checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tycon std_err = derivingThingErr cls cls_tys tc_app $ vcat [fromJust mb_std_err, - ptext SLIT("Try -XGeneralizedNewtypeDeriving for GHC's newtype-deriving extension")] + ptext (sLit "Try -XGeneralizedNewtypeDeriving for GHC's newtype-deriving extension")] -- Here is the plan for newtype derivings. We see -- newtype T a1...an = MkT (t ak+1...an) deriving (.., C s1 .. sm, ...) @@ -747,10 +845,10 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs -- Want to drop 1 arg from (T s a) and (ST s a) -- to get instance Monad (ST s) => Monad (T s) - -- Note [newtype representation] - -- Need newTyConRhs *not* newTyConRep to get the representation - -- type, because the latter looks through all intermediate newtypes - -- For example + -- Note [Newtype representation] + -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + -- Need newTyConRhs (*not* a recursive representation finder) + -- to get the representation type. For example -- newtype B = MkB Int -- newtype A = MkA B deriving( Num ) -- We want the Num instance of B, *not* the Num instance of Int, @@ -798,9 +896,10 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs right_arity = length cls_tys + 1 == classArity cls -- Never derive Read,Show,Typeable,Data this way - non_iso_classes = [readClassKey, showClassKey, typeableClassKey, dataClassKey] + non_iso_class cls = className cls `elem` ([readClassName, showClassName, dataClassName] ++ + typeableClassNames) can_derive_via_isomorphism - = not (getUnique cls `elem` non_iso_classes) + = not (non_iso_class cls) && right_arity -- Well kinded; -- eg not: newtype T ... deriving( ST ) -- because ST needs *2* type params @@ -841,19 +940,19 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs -- arguments must be type variables (not more complex indexes) cant_derive_err = derivingThingErr cls cls_tys tc_app - (vcat [ptext SLIT("even with cunning newtype deriving:"), + (vcat [ptext (sLit "even with cunning newtype deriving:"), if isRecursiveTyCon tycon then - ptext SLIT("the newtype may be recursive") + ptext (sLit "the newtype may be recursive") else empty, if not right_arity then - quotes (ppr (mkClassPred cls cls_tys)) <+> ptext SLIT("does not have arity 1") + quotes (ppr (mkClassPred cls cls_tys)) <+> ptext (sLit "does not have arity 1") else empty, if not (n_tyargs_to_keep >= 0) then - ptext SLIT("the type constructor has wrong kind") + ptext (sLit "the type constructor has wrong kind") else if not (n_args_to_keep >= 0) then - ptext SLIT("the representation type has wrong kind") + ptext (sLit "the representation type has wrong kind") else if not eta_ok then - ptext SLIT("the eta-reduction property does not hold") + ptext (sLit "the eta-reduction property does not hold") else empty ]) \end{code} @@ -903,7 +1002,7 @@ inferInstanceContexts oflag infer_specs iterate_deriv :: Int -> [ThetaType] -> TcM [DerivSpec] iterate_deriv n current_solns | n > 20 -- Looks as if we are in an infinite loop - -- This can happen if we have -fallow-undecidable-instances + -- This can happen if we have -XUndecidableInstances -- (See TcSimplify.tcSimplifyDeriv.) = pprPanic "solveDerivEqns: probable loop" (vcat (map pprDerivSpec infer_specs) $$ ppr current_solns) @@ -1041,50 +1140,41 @@ the renamer. What a great hack! -- Representation tycons differ from the tycon in the instance signature in -- case of instances for indexed families. -- -genInst :: OverlapFlag -> DerivSpec -> TcM (InstInfo, DerivAuxBinds) +genInst :: OverlapFlag -> DerivSpec -> TcM (InstInfo RdrName, DerivAuxBinds) genInst oflag spec | ds_newtype spec = return (InstInfo { iSpec = mkInstance1 oflag spec , iBinds = NewTypeDerived }, []) | otherwise - = do { fix_env <- getFixityEnv - ; let - inst = mkInstance1 oflag spec - (tyvars,_,clas,[ty]) = instanceHead inst - clas_nm = className clas - (visible_tycon, tyArgs) = tcSplitTyConApp ty + = do { let loc = getSrcSpan (ds_name spec) + inst = mkInstance1 oflag spec + (_,_,clas,[ty]) = instanceHead inst + (visible_tycon, tyArgs) = tcSplitTyConApp ty -- In case of a family instance, we need to use the representation -- tycon (after all, it has the data constructors) ; (tycon, _) <- tcLookupFamInstExact visible_tycon tyArgs - ; let (meth_binds, aux_binds) = genDerivBinds clas fix_env tycon - - -- Bring the right type variables into - -- scope, and rename the method binds - -- It's a bit yukky that we return *renamed* InstInfo, but - -- *non-renamed* auxiliary bindings - ; (rn_meth_binds, _fvs) <- discardWarnings $ - bindLocalNames (map Var.varName tyvars) $ - rnMethodBinds clas_nm (\_ -> []) [] meth_binds + ; fix_env <- getFixityEnv + ; let (meth_binds, aux_binds) = genDerivBinds loc fix_env clas tycon -- Build the InstInfo ; return (InstInfo { iSpec = inst, - iBinds = VanillaInst rn_meth_binds [] }, + iBinds = VanillaInst meth_binds [] }, aux_binds) } -genDerivBinds :: Class -> FixityEnv -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) -genDerivBinds clas fix_env tycon +genDerivBinds :: SrcSpan -> FixityEnv -> Class -> TyCon -> (LHsBinds RdrName, DerivAuxBinds) +genDerivBinds loc fix_env clas tycon | className clas `elem` typeableClassNames - = (gen_Typeable_binds tycon, []) + = (gen_Typeable_binds loc tycon, []) | otherwise = case assocMaybe gen_list (getUnique clas) of - Just gen_fn -> gen_fn tycon + Just gen_fn -> gen_fn loc tycon Nothing -> pprPanic "genDerivBinds: bad derived class" (ppr clas) where - gen_list :: [(Unique, TyCon -> (LHsBinds RdrName, DerivAuxBinds))] + gen_list :: [(Unique, SrcSpan -> TyCon -> (LHsBinds RdrName, DerivAuxBinds))] gen_list = [(eqClassKey, gen_Eq_binds) ,(ordClassKey, gen_Ord_binds) ,(enumClassKey, gen_Enum_binds) @@ -1092,7 +1182,7 @@ genDerivBinds clas fix_env tycon ,(ixClassKey, gen_Ix_binds) ,(showClassKey, gen_Show_binds fix_env) ,(readClassKey, gen_Read_binds fix_env) - ,(dataClassKey, gen_Data_binds fix_env) + ,(dataClassKey, gen_Data_binds) ] \end{code} @@ -1106,30 +1196,28 @@ genDerivBinds clas fix_env tycon \begin{code} derivingThingErr :: Class -> [Type] -> Type -> Message -> Message derivingThingErr clas tys ty why - = sep [hsep [ptext SLIT("Can't make a derived instance of"), + = sep [hsep [ptext (sLit "Can't make a derived instance of"), quotes (ppr pred)], nest 2 (parens why)] where pred = mkClassPred clas (tys ++ [ty]) +derivingHiddenErr :: TyCon -> SDoc +derivingHiddenErr tc + = hang (ptext (sLit "The data constructors of") <+> quotes (ppr tc) <+> ptext (sLit "are not all in scope")) + 2 (ptext (sLit "so you cannot derive an instance for it")) + standaloneCtxt :: LHsType Name -> SDoc -standaloneCtxt ty = ptext SLIT("In the stand-alone deriving instance for") <+> quotes (ppr ty) +standaloneCtxt ty = hang (ptext (sLit "In the stand-alone deriving instance for")) + 2 (quotes (ppr ty)) derivInstCtxt :: Class -> [Type] -> Message derivInstCtxt clas inst_tys - = ptext SLIT("When deriving the instance for") <+> parens (pprClassPred clas inst_tys) + = ptext (sLit "When deriving the instance for") <+> parens (pprClassPred clas inst_tys) badDerivedPred :: PredType -> Message badDerivedPred pred - = vcat [ptext SLIT("Can't derive instances where the instance context mentions"), - ptext SLIT("type variables that are not data type parameters"), - nest 2 (ptext SLIT("Offending constraint:") <+> ppr pred)] - -famInstNotFound :: TyCon -> [Type] -> Bool -> TcM a -famInstNotFound tycon tys notExact - = failWithTc (msg <+> quotes (pprTypeApp tycon (ppr tycon) tys)) - where - msg = ptext $ if notExact - then SLIT("No family instance exactly matching") - else SLIT("More than one family instance for") + = vcat [ptext (sLit "Can't derive instances where the instance context mentions"), + ptext (sLit "type variables that are not data type parameters"), + nest 2 (ptext (sLit "Offending constraint:") <+> ppr pred)] \end{code}